1. Field of the Invention
This invention relates to vitamin A palmitate compositions stabilized against crystallization at low temperatures and to emulsifiable concentrates thereof.
2. Description of the Prior Art
Vitamins have been used for many years as additives for animal feed to increase the rate of weight gain and to improve resistance to disease and overall performance of the animal. Because vitamins are used in very small amounts, additives in the form of vitamin concentrates and premixes are generally used to fortify the animal feed. Generally, the vitamins are added to the animal feed in the form of emulsifiable or solubilized solutions or dispersions of the vitamins. The fat-soluble vitamins must be emulsified or solubilized prior to introduction into the animal feed to prevent layering and segregation of the vitamins in the feed. Additionally, the vitamin additives should be pourable at temperatures below about 0.degree. C. in order that they may be useful in winter feeding programs in the northern and western states.
The fat-soluble vitamins, particularly vitamin A, in addition to having to be dispersed or emulsified prior to addition to feed, have the disadvantage in that they are characterized by having poor chemical stability. Their potency is lost upon exposure to air oxidation and/or exposure to water in the preparation of emulsions prior to addition to animal feed. It has, therefore, become the practice to provide non-aqueous, emulsifiable concentrates of vitamins, particularly vitamin A and other fat-soluble vitamins. When these concentrates contain animal feed and/or food additive-acceptable emulsifiers, the desired emulsion or dispersion can be prepared at the feed site. feed. Heretofore, the problem of providing an emulsifiable concentrate containing vitamin A which is stable at temperatures below the solidification temperature of vitamin A acetate or vitamin A palmitate in the pure state, has been solved by the use of various stabilization additives. These additives have included oxyalkylene compounds and short chain alkyl alcohols.
In U.S. Pat. No. 4,022,913, there are disclosed vitamin A acetate compositions stabilized against the formation of crystals at low temperatures (about 5.degree. C.) by the inclusion of vitamin A palmitate. This was unexpected in view of the fact that both vitamin A acetate and vitamin A palmitate in the pure state are solids at such temperatures.
In U.S. Pat. No. 3,639,587, there are disclosed non-aqueous vitamin-active preparations having crystallization temperatures below about 4.degree. C. which can include vitamin A. The compositions are stabilized against crystallization by the inclusion of a polyoxyethylene material and a viscosity reducing agent such as an ester of a lower alkyl alcohol.
In U.S. Pat. No. 3,708,583, there is disclosed a stabilized vitamin additive containing a mixture of vitamin A acetate and vitamin A palmitate in combination with a lower alkyl alcohol and a nonionic emulsifier.